Tuesday, September 18, 2012

The Other Side of Antimicrobial Resistance

An editorial was recently published by Bill Marler’s group entitled “Letter from the Editor: Antibiotic Resistance.”(1) For the most part, I agree with this article. However, there are a few points that I think need clarification. I will use a “point-counter point” approach, although not all of these counterpoints are arguments.

Point: “Antibiotics are integral in the treatment of many food-borne diseases, making this an important issue for the food safety community.”

Counter point: Yes, antimicrobial resistance (AMR) is a big deal. Antimicrobials are used in treating infections. However, they are not the first line of defense for treating food-borne illness, even in cases requiring hospitalization. Instead, the primary course of treatment is fluid therapy.(2) Therefore, even if we could erase AMR in food-borne pathogens, it is unlikely that there will be a significant improvement in the outcome of food-borne illness cases.

Point:

Drug-resistant infections take a staggering toll in the United States and across the globe. Just one organism, methicillin-resistant Staphylococcus aureus (MRSA), kills more Americans every year than emphysema, HIV/AIDS, Parkinson's disease, and homicide combined. Nearly 2 million Americans per year develop hospital-acquired infections (HAIs), resulting in 99,000 deaths - the vast majority of which are due to antibacterial-resistant pathogens. Two common HAIs alone (sepsis and pneumonia) killed nearly 50,000 Americans and cost the U.S. health care system more than $8 billion in 2006.

Counterpoint: The impact of AMR is staggering. Resistant infections have been a problem since the discovery of penicillin, which is the reason for the invention of multiple types of antibiotics.(3) It is also important to realize that very few of the bacteria listed in the above paragraph are related to livestock and food. In addition, several other medically important bacteria, such as Pseudomonas aeruginosa, Streptococcus pneumoniae, and Mycobacterium tuberculosis, have resistance patterns that cannot be explained from livestock antimicrobial usage.(4)

Point: “Antibiotics are becoming less and less effective, in part due to over-prescription and inappropriate use.”

Counter point: I don’t really disagree with this point but I would like to “fine tune” it a bit. As soon as an antibiotic is first used, resistance begins to develop. Bacteria evolve under the selection pressure of antibiotic exposure. It is how they survive. Inappropriate or unnecessary use means extra pressure on the bacterial population, thus increasing the speed of evolution.

To the extent that agriculture is guilty for antimicrobial resistance, we repent. It is important to note that many producer groups are making major efforts to become more prudent in antimicrobial use, just like what is being done in human medicine.

Point: “If I am reading scientists correctly, there are multiple theories for antibiotic resistance and agreement that some occurs naturally in the environment. Some of these theories involve antibiotic uses by both humans and animals.”

Counter point: Both points are correct. The ability to resist antibiotics has been around since the first microbe. Many types of antimicrobial resistance were recently discovered in four million year old dirt that had never been touched by man or beast.(5) Subsequently, any antimicrobial usage, even if appropriate, allows the resistant strains to become more prominent.

Point: “Yet, is it just me, or is antibiotics used in animal agriculture the only thing we hear about when antibiotic resistance comes up? Am I wrong to look at antibiotic resistance as a big circle with animal issues maybe involving a 25 percent slice with lots of other unknowns out there?”

Counter point: No counter argument here. You are correct! Agriculture is taking way too much of the heat for its contribution to antibiotic resistance, and all published risk assessments show this contribution to be negligible. I would venture to say the percentage is much less that 25%. One paper I published shows the average American is more likely to die from a bee sting (1 in 6 million) than to get a few extra days of diarrhea due to macrolide (a common animal antibiotic) use in livestock.(6,7)

Point: “I just have this feeling that allowing animal diseases to go untreated would not contribute to food safety.”

Counter point: Again, I agree. Failure to treat or prevent illness leads to needless animal suffering. Additionally, some new research is showing that healthy animals that have recovered from a respiratory or infectious illness are more likely to be contaminated with foodborne pathogens such a Salmonella or Campylobacter.(8,9)

Point: “Antibiotic resistance is complex issue. Help direct our coverage by suggesting people we should talk to and places we should go. Where's the cutting edge research being done? This is not just some problem on the farm we haven't solved. It's bigger, broader, and more complex. Now, please submit your answers.”

Counter point: Amen brother. There many questions that have not been addressed. If society was not so busy pushing draconian and meaningless solutions such as the PAMTA (Preservation of Antibiotics for Medical Treatment Act) or collecting usage data without good data on resistance, then resources would be available to answer many of your thoughtful questions.